Question

In the Lord of the Rings, watchtowers with bright lights were placed on mountain ranges to signal one city's need for help from another.

A modern string of such towers equipped with relay lasers is placed 100 km apart in a straight line (you may ignore earth curvature), and automated circuits relay the optical signal by turning on the next signal within 0.19 ms. Thus, the time it takes a signal to cross a continent 1900 km wide includes the reaction time for the relay and the time for the light to cross from one tower to the next. What fraction of the total time to get the signal across, starting with when the first laser starts shining, is taken by the total time light is traveling from tower to tower?

(Enter your answer as a percentage, without the '%' sign, to at least two significant figures.)

Answer 1